A billhook is a sort of agricultural/forestry tool which was used for pruning vines, fruit trees, and shrubs. It consisted of a heavy blade which twisted into a cruel sharpened steel hook (like a parrot’s bill), all of which was, in turn, attached to a wooden handle—or sometimes to a long staff for pruning hard to reach branches. At some point in the late middle ages, it was noted that this alarming tool could be used to prune a wider range of targets than just unruly fruit trees: suddenly the billhook evolved into a sinister polearm (admittedly, the Chinese had some similar cavalry hooks, but we are talking about the European/English bill in this article).
The bill was a powerful weapon with the range of a spear and the brute chopping power of an axe. It could be used like a pike to stop a cavalry charge (or hack/stab swordsmen before they reached the wielder) it also had a hook to snatch horsemen from their mounts or take enemy combatants’ legs out from beneath them.
The bill came to prominence in the 14th and 15th centuries as the Middle Ages waned. Soldiers using bills were called billmen and usually wore chainmail or plate armor. Often they also wore sallets, the helmets of the day, which could be open faced or have visors. Generally billmen also were attired with colorful tabards over their armor (often with all sorts of heraldic emblems) and bright tights or leggings. High status soldiers would have big dyed feathered plumes on their helmets. These were some impressive & flamboyant foot soldiers!
In continental Europe the early 16th centuries saw armies moving towards the pike and the arquebus (a sort of nightmarish early musket), however the English preferred to rely on the rapid fire of their hallowed longbow. And for infantry, they still favored bills over pikes—a choice which turned out to be a good one. In the Battle of Flodden, which occurred in 1513, an army of approximately 26,000 English billmen chopped apart a larger army of Scottish pikemen. The Scottish king, James IV was hacked apart right along with his soldiers and was the last monarch of the British Isles to die in glorious combat (so far).